An ultrasound system has become an important and popular diagnostic tool since it has a wide range of applications. Specifically, due to its non-invasive and non-destructive nature, the ultrasound system has been extensively used in the medical profession. Modern high-performance ultrasound systems and techniques are commonly used to produce two or three-dimensional ultrasound images of internal features of a target object (e.g., human organs).
To provide the ultrasound images, the ultrasound system operates in various image modes such as a brightness mode (B mode), a Doppler mode and the like to acquire ultrasound images for diagnosis.
In the Doppler mode, the ultrasound system provides a color Doppler mode image showing velocities of moving objects such as the heart, blood flow, etc. The color Doppler mode image may be formed based on Doppler signals obtained by alternately transmitting and receiving ultrasound signals to and from a target object. The Doppler signals may include a low frequency signal (so-called clutter signal) due to the motion of a cardiac wall or valve of a heart. The clutter signal may have an amplitude which is over 100 times greater than that of pure Doppler signals indicative of velocities of the blood flow. The clutter signal may be an obstacle for accurately detecting the velocity of blood flow. Thus, it is required to remove the clutter signal from the Doppler signals for an accurate velocity detection of the blood flow. The ultrasound system typically adopts a clutter filter that may be a high pass filter, an eigenvector-based clutter filter, a singular value decomposition (SVD) clutter filter and the like to remove the clutter signal from the Doppler signals.